Doren et al, in an U.S. Pat. application entitled "DATA PROCESSING SYSTEM WITH LOGICAL PROCESSOR FACILITY", filed Nov. 12, 1986, Ser. No. 930,965, and owned by the assignee of the present invention, disclose a multi-user data processing system wherein each user is given the control of a domain of facilities. The user operates within the user's domain as though the user had control of a separate logical computer, so that the data processing system functions as multiple data processing systems.
The features of a data processing system, such as, for example, its maximum memory size or the allowable types of input/output channel operations, are often sold or leased as options. Therefore, it is often desirable to be able to control features of a data processing system. In data processing systems similar to that described by Doren et al, one such important feature is the number of domains that can be initiated concurrently in the system. Controlling the number of domains is desirable, for example, when a system installation is charged for the maximum number of domains that can be activated concurrently or when it is desirable to guarantee a minimum level of performance of the domains by regulating system resources contention.
In typical prior art data processing systems, controlling a feature of a system is achieved by storing an authorization code in a "hidden" location of the main memory. (The authorization code may be, for example, the maximum number of domains that can be started concurrently.) To change the feature of the system, a key code (which, under the above example, the key code will be the number of domains already activated in the system) will be checked against the authorization code. The feature operation will be changed when the check is successful.
One disadvantage of the above-described method is that because the authorization code is stored in the main memory, it can easily be tampered with.
An object of this invention is to provide a more secure method and apparatus for controlling the features of a data processing system, especially for controlling the number of domains which can be initiated in a multi-domain system.